Ten days in Colonial Mexico sounds like a great trip. And already you've had some wonderful feedback. Plus the Moon Handbooks are very good. However, for your purposes I'd suggest getting the Central Mexico Handbook. There is a bit of overlap between it and the Pacific Mexico book that you have but it will be much more specific for your needs.

I agree with Judy's suggestion of a couple of days seeing Guadalajara. Unfortunately, I haven't visited Guadalajara in years (soon though) so my suggestions are very general. The Mercado Libertad is one of the largest in Mexico and an absolute must. Mariachis and tequila are worth investigating here as this is the Mecca for both. The International Mariachi Festival is held here every year from August to September. The gala performances are held at the Teatro Degollado. The theater is gorgeous and should be visited. I believe there is a ballet folklorico performing there several times a week. For tequila you can take the Tequila Train out to the town of Tequila or go by bus and visit one of the distelleries.

From Guadalajara you have a few choices. As Judy said San Miguel de Allende would be a reasonable central location. It is 5 hours by bus from Guadalajara. Air travel is not really an option. The major airport for this part of Mexico is in the city of Leon which will only get you about half way to San Miguel. You might consider staying in Guanajuato (about 3.5 hours by bus from Guadalajara). Many consider it to be the archetype of the colonial Mexico city. No matter which one you choose you'll be well situated to visit the other towns and cities of the Bajío (the name given to this part of Mexico).

Morelia is only about 3.5 hours from Guadalajara but to the south east as opposed to directly east for the Bajío). Morelia has a lot to offer and could keep you interested for the remainder of your trip if you include visits to Pátzcuaro, the monarch butterfly forests, and Uruapan. But I think you would probably want to spend a couple of days in Morelia and then relocate to Pátzcuaro. But I wouldn't recommend trying to include Morelia in with the Bajío. Just too far away.

My inclination is to suggest you visit the Bajío (Guanajuato, San Miguel de Allende, Dolores Hidalgo, etc.). This is the area that best matches people's idea of colonial Mexico (although every part of Mexico has colonial elements). Then if you enjoy yourselves come back and visit Morelia and Pátzcuaro for an introduction into the indigenous cultures within Mexico, in this case the Purépecha. Then it is on to Oaxaca, the Yucatan, Chiapas...

An excellent website with lots of info and links for aiding the independet traveler in Mexico is http://www.ourmexico.com/index.php

Good luck with your research. For more help just ask. John in San Diego